Verwijdering van fosfaat uit bodemwater met ijzerzand : De omhulde drain

In het Nederlandse oppervlaktewater zijn de fosfaatconcentraties vaak te hoog en vormt eutrofiëring een groot probleem. Fosfaatuitspoeling uit landbouwgronden draagt flink bij aan de totale fosfaatbelasting van het oppervlaktewater. Met brongerichte maatregelen, zoals evenwichtsbemesting, zal in sommige delen van het landelijk gebied de hoofddoelstelling van de Kaderrichtlijn Water niet worden gerealiseerd. Hiervoor zijn aanvullende maatregelen nodig, die kunnen bijdragen aan het verbeteren van de chemische waterkwaliteit. We hebben de effectiviteit getest van een drainagebuis omhuld met ijzerzand om fosfaatuitspoeling te verminderen. Deze veldproef is uitgevoerd op een duinzandgrond in het bloembollengebied. Het gemiddelde zuiveringsrendement van de omhulde drainagebuis bedraagt 94 procent. Het omhullen van drainagebuizen met ijzerzand lijkt een veelbelovende maatregel voor het verminderen van fosfaatuitspoelin

Long-term risks of inadequate management practices on the sustainability of agricultural soils

This report describes the major result of a research project funded by the INCO-Copernicus programma of European Commission under Contract number ERB-IC15-CT98-0133. The study focused on the long-term environmental risk of soil acidification on: (i) mobilisation and leaching and (ii) plant uptake of potentially toxic heavy metals (i.e. lead, cadmium, zinc and copper) from well-drained agricultural soils in Slovakia and Hungary. The research was mainly carried out in the period 1998-2001, but there was a strong delay in the final reporting of the results as summarised in this report. This report includes the major papers resulting from this study. The major result obtained from the various studies is that transfer functions and soil-to-plant transfer relationships, allowing the calculation of dissolved metal concentrations and plant meta contents from soil metal contents accounting for differences in soil properties, such as pH and organic matter content, in the solid phase, are practical and reasonably reliable approaches for use in regional risk assessments, as carried out for Hungary and Slovakia

Modelling the response of soil and soil solution chemistry upon roofing a forest in an area with high nitrogen deposition

In the Speuld forest, the Netherlands, the dynamic soil acidification model NuCSAM has been applied to a manipulation experiment in which part of the forest was roofed to control nitrogen (N) and sulphur (S) deposition. The roofed area was divided into two subplots watered artificially; one received ambient N and S deposition and one with pristine N and S deposition. Concentration measurements on each plots showed a high (time-dependent) spatial variability. Statistical analyses of the concentrations on both subplots showed small but significant effects of the reduction in deposition on nitrate (NO3) sulphate (SO4) and aluminum (Al) concentrations. The statistical significance of the effects was minimised by the large spatial variability within the plots. Despite these shortcomings, simulated concentrations were generally within the 95% confidence interval of the measurements although the effect of a reduction in N deposition on soil solution chemistry was underestimated due to a marked decline in N-uptake by the vegetation

Bodembescherming bij doorgangsdepots voor baggerspecie : Verwaarloosbaar bodemrisico met een geochemische barrière

Bij het ontwateren en rijpen van nuttig toepasbare baggerspecie wordt veelvuldig gebruikt gemaakt van doorgangsdepots. Op initiatief van de waterschappen is een alternatief ontwikkeld voor de bodembescherming met behulp van een folie. Met een minerale bodembeschermingslaag kan eveneens een verwaarloosbaar bodemrisico bereikt worden. Een generieke regeling bleek vooralsnog niet haalbaar

Assessment of relationships between total and reactive concentrations of cadmium, copper, lead and zinc in Hungarian and Slovakian soils

To account for the difference between the total metal pool and the biologically available pool, a wide range of mild extracts have been proposed to estimate plant uptake. Despite numerous sequential extraction schemes, specific information on the availability of those pools in view of its relation with dissolved concentrations, readily available for plant uptake or leaching to groundwater is lacking. This stresses the need for a single extraction that is able to evaluate the reactive (potential available) metal content in different soils, that can be related to the dissolved metal concentration. In this study a single, dilute acid extraction by 0.43 mol.1(-1) HNO3 was applied on 72 soil samples that are representative for Hungary (33 plots) and Slovakia (39 plots). Sampling was limited to the plough layer where most effects on solute uptake (and ecology) are to be expected, i.e. within 0-20 cm. The soil samples were also extracted with EDTA to compare the results obtained with the mild HNO3 extraction. Furthermore, the "so-called total" metal content was measured by using an aqua regia extraction. The samples included a large range in soil properties and degree of contamination, the latter by including 12 plots from a long-term field experiment with heavy metals in Hungary. The main purpose of this study was to investigate the possibility to derive reactive metal contents from "so-called total" metal contents, the latter being readily available for a large number of plots in many countries. Results showed a considerable agreement between reactive metal concentrations measured with a mild (0.43 mol.h(-1)) HNO3 extraction and with an EDTA extraction. Furthermore, a considerable part of the metals are present in a rather unavailable form in soils. On average, Zn has the lowest reactive to total metal ratio (0.17), followed by Pb (0.30), Cu (0.38) and Cd (0.56). For each metal considered there is a large range in ratios of reactive to total metal content. On average, a reasonable prediction can be made of reactive metal contents from total metal contents and the organic matter and clay content using regression relations. However, large errors can be made for individual samples specifically in the low concentration range. The derived relations are further completely empirical and can only to be used for the types of soil for which they were derived

Application of the model NUCSAM to the Solling spruce site

The Nutrient Cycling and Soil Acidification Model (NUCSAM) was applied to a spruce site at Solling, Germany, within the scope of a workshop on comparison of forest soil-atmosphere models. Simulated trends and dynamics in the concentrations of sulphatealuminium and pH between 1970 and 1990 compared favourably with time-series of measured data during that period. Dynamics and concentrations of nitrate in the subsoil were overestimated. Simulation results for the period 1990-2090 for two deposition scenarios showed ongoing acidification (pH decrease) of the soil at the present acid load and a rapid response of soil solution chemistry to reduced acid input, but there was a long time delay before favourable Al/Ca ratios were reached

Application of the model NUCSAM to the Solling spruce site

The Nutrient Cycling and Soil Acidification Model (NUCSAM) was applied to a spruce site at Solling, Germany, within the scope of a workshop on comparison of forest soil-atmosphere models. Simulated trends and dynamics in the concentrations of sulphatealuminium and pH between 1970 and 1990 compared favourably with time-series of measured data during that period. Dynamics and concentrations of nitrate in the subsoil were overestimated. Simulation results for the period 1990-2090 for two deposition scenarios showed ongoing acidification (pH decrease) of the soil at the present acid load and a rapid response of soil solution chemistry to reduced acid input, but there was a long time delay before favourable Al/Ca ratios were reached